---
title: "Changes to Starts an experiment immediately."
method: POST
path: "/creator-configs-public-api/v1/experimentation/universes/{universeId}/experiments/{experimentId}:start"
---

# Changes to Starts an experiment immediately.

`POST /creator-configs-public-api/v1/experimentation/universes/{universeId}/experiments/{experimentId}:start`

> Every recorded change to this operation, newest first.

## Timeline

Changed in 3 of 33 revisions.

- **2026-10-22** `bcfdc20689cd`: 4 breaking, 1 info
- **2026-09-17** `7c6787738100`: 1 warning
- **2026-08-19** `1d2042bb1a48`: 1 info

## Changes

- **2026-10-22** `bcfdc20689cd`: 4 breaking, 1 info
  - the `operation/allOf[#/components/schemas/ExperimentOperation]/experiment/allOf[#/components/schemas/ProductExperiment]/targetingCriteria/allOf[#/components/schemas/TargetingCriteria]/rule/allOf[#/components/schemas/ConditionalRuleDefinition]/tokens/items/operand/allOf[#/components/schemas/RpnOperandDto]/literalValue/allOf[#/components/schemas/LiteralValueDto]/booleanValue` response's property type changed from `string` to `boolean` for status `200`
  - the `operation/allOf[#/components/schemas/ExperimentOperation]/experiment/allOf[#/components/schemas/ProductExperiment]/targetingCriteria/allOf[#/components/schemas/TargetingCriteria]/rule/allOf[#/components/schemas/ConditionalRuleDefinition]/tokens/items/operand/allOf[#/components/schemas/RpnOperandDto]/literalValue/allOf[#/components/schemas/LiteralValueDto]/doubleValue` response's property type changed from `string` to `number`, and format from no format to `double` for status `200`
  - the `operation/allOf[#/components/schemas/ExperimentOperation]/experiment/allOf[#/components/schemas/ProductExperiment]/targetingCriteria/allOf[#/components/schemas/TargetingCriteria]/rule/allOf[#/components/schemas/ConditionalRuleDefinition]/tokens/items/operand/allOf[#/components/schemas/RpnOperandDto]/literalValue/allOf[#/components/schemas/LiteralValueDto]/integerValue` response's property type changed from `string` to `integer`, and format from no format to `int64` for status `200`
  - the `operation/allOf[#/components/schemas/ExperimentOperation]/experiment/allOf[#/components/schemas/ProductExperiment]/targetingCriteria/allOf[#/components/schemas/TargetingCriteria]/rule/allOf[#/components/schemas/ConditionalRuleDefinition]/tokens/items/operator` response's property type changed from `string` to no type for status `200`
  - added `#/components/schemas/ConditionalRuleOperator` to the `operation/allOf[#/components/schemas/ExperimentOperation]/experiment/allOf[#/components/schemas/ProductExperiment]/targetingCriteria/allOf[#/components/schemas/TargetingCriteria]/rule/allOf[#/components/schemas/ConditionalRuleDefinition]/tokens/items/operator` response property `allOf` list for the response status `200`
- **2026-09-17** `7c6787738100`: 1 warning
  - added the new `EXPERIMENT_API_ERROR_TYPE_CONFIGS_KEY_HAS_RESERVED_PREFIX` enum value to the `operation/allOf[#/components/schemas/ExperimentOperation]/error/allOf[#/components/schemas/ExperimentApiError]/errorType/allOf[#/components/schemas/ExperimentApiErrorType]/` response property for the response status `200`
- **2026-08-19** `1d2042bb1a48`: 1 info
  - endpoint added

---

[Operation](https://skmtc.dev/roblox/apis/roblox-api/docs/creator-configs-public-api/v1/experimentation/universes/:universeId/experiments/:experimentId:start/post.md) - [API](https://skmtc.dev/roblox/apis/roblox-api.md) - [Page](https://skmtc.dev/roblox/apis/roblox-api/changes/creator-configs-public-api/v1/experimentation/universes/:universeId/experiments/:experimentId:start/post)